Japanese Patent Application Laid-open No. 7-25303 discloses an airbag device in which an inner bag having four branch parts branching from a collecting part connected to an inflator is integrally sewn onto an inner surface of a bag body having an air supply/discharge hole, and a gas is supplied to the branch parts of the inner bag to inflate the inner bag, thereby giving tension to the bag body to take in the external air through the air supply/discharge hole to inflate the bag body. According to this airbag device, it is possible to inflate the bag body by only inflating the inner bag by supplying the gas, and therefore the inflator can be made compact.
However, in the above-described conventional airbag device, the base cloth of the inner bag which is inflated by inflow of the gas is sewn integrally onto the base cloth of the bag body to form a closed space, resulting in a problem that the manufacturing process is complicated to increase the cost, as compared with the case where the inner bag and the bag body are individually sewn.
The present invention has been achieved in view of the above-mentioned circumstances, and its object is to provide an airbag device capable of quickly deploying an airbag with a compact inflator and easy to manufacture.